fix one bubble test based on arbitrary order
fix one bubble test based on arbitrary order

for #934

TheDataShed/dc.js,mtraynham/dc.js,dc-js/dc.js,TheDataShed/dc.js,mtraynham/dc.js,aaronhoffman/dc.js,aaronhoffman/dc.js,aaronhoffman/dc.js,TheDataShed/dc.js,TheDataShed/dc.js,mtraynham/dc.js,dc-js/dc.js,mtraynham/dc.js,TheDataShed/dc.js,dc-js/dc.js,dc-js/dc.js,mtraynham/dc.js,aaronhoffman/dc.js,dc-js/dc.js,aaronhoffman/dc.js